制备方法对稀土金属钇改性Ni_2P催化剂结构及其加氢脱硫性能的影响

采用一步法和分步法制备了钇(Y)改性的非负载型Y_x-Ni_2P催化剂(x为Y和Ni的物质的量比),并采用X射线衍射(XRD)、N_2吸附比表面积(BET)测定、X射线光电子能谱(XPS)技术对催化剂的结构和性质进行了表征。以二苯并噻吩(DBT)为模型化合物,研究了制备方法对Y_x-Ni_2P催化剂加氢脱硫(HDS)性能的影响。结果表明,Y改性可以抑制Ni5P4杂晶相的生成,促进Ni_2P活性相的生成,能显著提高催化剂的比表面积和孔容,从而有效提高磷化镍催化剂的HDS活性。Y/Ni物质的量比为0.10时,两种方法制备的催化剂均具有最高的HDS活性。与分步法相比,一步法制备得到的催化剂具有更大的比表面积和孔容,更小的表面P/Ni物质的量比,更高的CO吸附容量,暴露出更多的Ni活性位点,从而具有更高的HDS活性。在340℃,3.0 M Pa,H_2/油体积比为700,质量空速(WHSV)1.5 h~(-1)的条件下,一步法制得的Y_(0.10)-Ni_2P催化剂上DBT HDS转化率达到97.7%,与分步法制备的Y_(0.10)-Ni_2P催化剂相比(92.3%),HDS活性提高了5.4%。

Effect of preparation method on the structure of rare earth metal Y modified Ni2P catalysts and its HDS performance

The yttrium (Y) modified unsupported Y_x-Ni₂P catalysts were prepared by one step method and stepwise method (x refers to mol ratio of Y to Ni), respectively.The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption specific surface area measurements (BET), CO uptake and X-ray photoelectron spectroscopy (XPS).The effects of preparation methods on thehydrodesulfurization (HDS) property of the catalysts were investigated by using dibenzothiophene (DBT) as the model compound.The results show that the addition of Y can suppress the formation of Ni₅P₄ phase and thus promote the formation of active Ni₂P phase.The addition of Y can dramatically increase the surface area and pore volume, effectively improve the HDS activity of nickel phosphide catalyst.The Y_x-Ni₂P catalysts prepared by these two methods with Y/Ni mol ratio of 0.10 exhibited the highest HDS activity.As compared to the stepwise method, the one step method which obtained catalysts possessed a larger specific surface area with high pore volume, a lower surface P/Ni mol ratio, a larger CO uptake and more exposed active Ni sites as compared to stepwise method.As a result, it showed a higher HDS activity.At a temperature of 340℃, a pressure of 3.0 MPa, a H₂/oil volume ratio of 700 and a weight hourly space velocity (WHSV) of 1.5 h^-1, the conversion of DBT over Y_0.10-Ni₂P catalyst prepared by one step method reached 97.7%, which was an increase of 5.4% comparing with the Y_0.10-Ni₂P catalyst prepared by stepwise method (92.3%).